River Engineering and
Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia has been
appointed to provide consultancy services for the drainage works as part of
Civil and Structure components for the proposed “Cadangan Mendirikan Sebuah
Klinik Kesihatan Taiping – 2 Tingkat (Jenis KK2) Di Atas Lot 2089, Jalan
Tupai, Mukim Tupai, Daerah Larut & Matang, Perak Darul Ridzuan”. In this
project the Government is planning to construct a drainage system to comply
with the new guidelines of Department of Irrigation and Drainage (DID),
Urban Stormwater Management Manual for Malaysia (MSMA).

PROJECT
BACKGROUND

The Government of Malaysia
via Public Works Department (JKR) Malaysia has planned to construct a new
building for the Taiping Town Clinic and its infrastructure on the area
approximately 7 acres in Larut & Matang District in Perak. This project
consists of the construction of a double storey building block, chemical
store, condenser block, TNB block, store and garage, security guard house,
sewerage treatment plant, pavilion and car park. The soil profile for
overall project area is consistent from silty sand at the first 10m depth to
hard layer of silty clay. Ground water level is observed at 0.95m to 1.35m
depth from original ground surface.

PROPOSED
DRAINAGE SYSTEM

The proposed drainage
system which is known as Bio-Ecological Drainage System (BIOECODS) is
consistent with objectives of new stormwater management approach which focus
on the control of both the quantity and quality of urban runoff. This has
been embodied in the concept of ecologically sustainable development which
is aimed at ensuring that development can occur without long-term
degradation of natural resources and the environment.

The new stormwater
management approach, BIOECODS, based on set of broad and holistic
principles for effective stormwater environment management:

·The
establishment of a storage-oriented approach for controlling runoff
quantity from development sites;

·The
identification of the environmental values (or benefits uses) of
particular water bodies which are to be protected;

·The
establishment of objectives which will achieve required levels of flood
protection and water quality enhancement;

·The
establishment of water quality management strategies;

·The
development and implementation of monitoring and surveillance programs
to ensure that runoff quantity and water quality (or environmental)
objectives are being maintained; and

·The
implementation of research programs to gain a better understanding of
the behavior of aquatic systems in order to improve water quality design
and management technique.

Figure 1 Layout Plan
for Proposed Drainage System

By integrating stormwater
management planning with landscape and environmental planning, it will add
aesthetic and recreational values to the water amenities. This site is
planned to become a showpiece of the new drainage system for the Perak State
and will also provide the database to support the new stormwater management
manual as we still lack of data for local conditions and to evaluate the
effectiveness of the stormwater runoff quantity and quality control system.

PROPOSED
DRAINAGE LAYOUT

The proposed drainage
system has several runoff control facilities to regulate the runoff from the
site as shown in Figure 1. The receiving waterway is made up of an upgraded
covered concrete lined drains before discharging to River Batu Tugoh
nearby.

Figure 2 Design Concept of Proposed Drainage System

Figure 3 Typical Section for Grassed Swale

Figure 4 Typical Section for Underground Detention Storage

DESIGN
CONCEPT

The new
environmental-friendly drainage system, BIOECODS, uses “control at
source” principle simulating the natural hydrological cycle in urban
areas by combining infiltration, detention storage, retarded flow as
well as runoff treatment techniques. Among the stormwater facilities
provided are grassed swale, underground detention storages and dry
ponds. The design concept is given in Figure 2.

a)
Grassed Swale (Figure
3)

Grassed
swale is designed to cater any excess water from perimeter drain (for
individual building) whilst the flow from pervious and impermeable
surface will be directed to the grassed swale. The grassed swale is
defined as grass earth channel combined with subsurface module which
enclosed within a permeable geotextile. Grassed swale has the ability to
reduce on-site peak flow rates by increasing the roughness of the
channel and infiltration rates. These vegetated systems also provide
runoff quality treatment by removing low concentrations and quantities
of TSS, heavy metals, hydrocarbons and nutrients from stormwater. The
vegetated systems remove pollutants by means of sedimentation,
filtration, soil absorption and plant uptake.

b)
Detention Storage (Figure
4)

The
excess stormwater is stored in the subsurface detention storage. The
storage modules have been designed to be places at the connecting
points, junction and critical point of the system. These detention
storages are provided to reduce flows from the building, regulating flow
velocity which causes the gravity settling of particulates and increase
the infiltration process where all these mechanisms will control the
quality and quantity of stormwater runoff.

c) On-site Stormwater Detention (OSD)

The
excess stormwater is also stored in the dry pond constructed with a
storage function. The dry pond is a detention basin with the purpose to
temporary store the stormwater runoff. This detention basin is design to
store to the surface of 600mm of the excess rainfall under design
average recurrent interval of 10-year and blend with the surrounding
landscape. The outflow path is controlled by orifices in order to drain
the dry pond system in less than 24 hours. Therefore, the quantity and
quality of the runoff from developed areas can be maintained to be the
same as pre-development condition. OSD is normally dry or empty when not
in operation. It will be utilized for multi-purpose use to incorporate
passive and active recreational areas such as public parks and open
space or sporting facilities.

SUMMARY

The proposed BIOECODS
is an applicable concept that will fulfill new urban stormwater
management objectives to restore each component of the hydrological
cycle to its natural level. This new stormwater management approach has
taken into broad consideration with the purposes:

to provide
safety for the public,

to
minimize and control nuisance flooding,

to stabilize the
landform and erosion control,

to enhance
the urban landscape, and

to
minimize the environmental impact of urban runoff on water quality.

ACKNOWLEDGEMENT

REDAC would like to
thank Public Works Department (JKR) for the opportunity to participate in
this project.